The disclosure relates generally to distribution of communications signals in a distributed antenna system (DAS), and more particularly to offsetting unwanted downlink interference signals in an uplink path in a DAS resulting from a shared antenna for downlink and uplink communication in a remote antenna unit (RAU).
Wireless customers are increasingly demanding digital data services, such as streaming video signals. Concurrently, some wireless customers use their wireless devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs can be particularly useful when deployed inside buildings or other indoor environments where client devices may not otherwise be able to effectively receive radio frequency (RF) signals from a source. DASs include RAUs configured to receive and transmit communications signals to client devices within the antenna range of the RAUs.
A typical DAS includes head-end equipment (HEE) communicatively coupled to a plurality of RAUs. The HEE is connected to receive a variety of wireless services for distribution to the RAUs, such as wideband code division multiple access (WCDMA), long term evolution (LTE), and wireless local area network (WLAN) communications services, as examples. To distribute such wireless communications services in a DAS, the wireless communications services can be provided in the form of analog RF communications signals and/or digital communications signals to the HEE of the DAS for distribution to the RAUs.
An RAU in the DAS may be configured to support more than one type of wireless service that operates in a variety of RF spectrums and bandwidths. Downlink wireless communications signals received by the RAU are typically amplified by a power amplifier to increase the signal strengths before distributing the downlink wireless communications signals to client devices through one or more coupled antennas. However, the amplified downlink communications signals may include a plurality of interference products. For example, these interference products may be created as a result of non-linearities of the power amplifier in the downlink path. For instance, if two downlink wireless communications signals operating on 850 MegaHertz (MHz) and 870 MHz bands, respectively, are amplified by a power amplifier, a plurality of interference products may be generated below the 850 MHz band (e.g., 830 MHz, 810 MHz, 790 MHz, and so on) and above the 870 MHz band (e.g. 890 MHz, 910 MHz, 930 MHz, and so on). Hence, the interference products should be sufficiently isolated to prevent or reduce interferences on adjacent wireless communication channels.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.